Apparatus for adjusting the relative inclinations of pivotable members

ABSTRACT

This invention relates to apparatus for controlling the inclination of a pivotable member relative to a fixed structure, in particular the inclination of the jib of a crane. Control is effected by two jacks, each being connected by one end to the jib and by the other end to the body of the crane. The points of attachment of the jacks to the jib and the pivot axis of the jib define the vertices of two deformable triangles, one preferably being right-angled when the other has been flattened to a straight line. The lifting torque of a crane can thereby be substantially constant for all values of jib inclination.

nite States Patent 11 1 Bourges 1 1 APPARATUS FOR ADJUSTING THE RELATIVEINCLINATIONS OF PIVOTABLE MEMBERS Bernard M. Bourges, Lagny Le Sec,France [75] Invento 173] Assignee: Societa Anonyme Poclain, Oise,

France 22 Filed: July 17, 1974 21 Appl.No :489,099

214/130 R, 77 R; 212/8 R, 8 A, 9, 35 R, 35 HC, 58 R, 58 A, 59 R, 59 A,66; 91/210, 411 R, 413; 180/792 B; 254/124; 74/36, 128, 42,

[56] References Cited UNITED STATES PATENTS 2,841,231 7/1958 ArmingtonISO/79,2 B

[4 1 Aug. 19, 1975 Primary E.\'anzinerAlbert J. Makay AssistantExuminerLawrence J. Oresky Attorney, Agent, or Firm-Fitzpatrick, Cella,Harper & Scinto [57] ABSTRACT This invention relates to apparatus forcontrolling the inclination of a pivotable member relative to a fixedstructure, in particular the inclination of the jib of a crane. Controlis effected by two jacks, each being connected by one end to the jib andby the other end to the body of the crane. The points of attachment ofthe jacks to the jib and the pivot axis of the jib define the verticesof two deformable triangles, one preferably being right-angled when theother has been flattened to a straight line. The lifting torque of acrane can thereby be substantially constant for all values of jibinclination.

PATENTEI] Am; 1 9197s SE'IET E OF 2 APPARATUS FOR ADJUSTING TI-IERELATIVE INCLINATIONS OF PIVOTABLE IVIEMBERS This invention relates toapparatus for controlling the inclination ofa pivotal member on a fixedstructure, for instance the jib of a lifting machine or a Public Worksmachine.

The jib of a hydraulic shovel is usually pivoted to a frame or turretthereof, and changes in the inclination of the jib are effected by ahydraulic jack connected be tween the jib and the turret. This jack isusually in the acute angle which the jib makes with the horizontal. Thedisadvantage of apparatus of this kind is that the torque applied at thefoot of the jib, that is the point about which the jib is pivoted to theturret, is not constant. If the hydraulic pressure acting on the jack isconstant, this torque is proportional to the length of the lever arm tothe end of which a force is applied. This lever arm is equal to thedistance between the point about which the foot of the jib is pivoted tothe frame and the line of action of the jack. It is therefore variableby reason of movement of the jack with respect to this point. Thevariation in torque is substantially sinusoidal, which is a disadvantageas it limits the possible uses of the machine. It is in fact always moreprofitable to make a machine operate at the limits of its capabilities,and these are determined by its design and are represented moreparticularly by the rocking torque. The rocking torque is substantiallyconstant, and with hith erto proposed machines it is impossible tooperate very close to this torque at all positions of the jib.

According to the present invention there is provided apparatus forchanging the inclination of a pivotal element, the element being pivotalabout an axis with re spect to a fixed structure, the apparatuscomprising a main jack connected between the structure and the element,and a secondary jack connected between the structure and the element,the main jack always being on the same side of said pivotal axis, thepoints of connection of the respective jacks to said structure and saidelement, and said pivotal axis constituting the vertices of twodeformable triangles, the defonnable triangle of which one side isdefined by the secondary jack being flattened to form a straight linewhen the deformable triangle of which one side is defined by the mainjack is substantially right-angled at its vertex defined by the point ofattachment of said main jack to said structure.

In a preferred embodiment of the invention said jacks are hydraulic anddouble-acting, and each chamber thereof communicates with a circuit fordistributing and returning a fluid under pressure, the communicationbeing direct in the case of the main jack and through distribution andreversing means in the case of the secondary jack, said distribution andreversing means being controlled by detector means responsive to theposition of the secondary jack with respect to said pivotal element.

In accordance with a further preferred embodiment of the presentinvention, said detector means comprises a lug rigid on an end portionof the secondary jack the lug being arranged to cooperate with a camconnected to the slide valve of the said distributing and reversingmeans, said cam being capable of assuming two stable positions under theaction of said lug, the stable positions being maintained by resilientreturn means, the two stable positions corresponding respectively topositions of the secondary jack on one or other side of the line definedby the said flattened triangle.

One embodiment of the present invention will now be described, by way ofexample, with reference to the accompanying diagrammatic drawings, inwhich:

FIG. 1 shows a hitherto proposed machine;

FIG. 2 shows graphically the variations in characteristic torques of amachine as shown in FIG. 1;

FIG. 3 shows an embodiment in accordance with the invention; and

FIG. 4 graphically shows the variations in characteristic torques of amachine including an embodiment as shown in FIG. 3. I

FIG. 1 shows a hydraulic shovel with a structure 1 consisting of aturret 1b rotatable on a frame la. A jib 2 on structure 1 is pivotalabout an axis 3. Between jib 2 and structure 1 is ajack 4 which isconnected to two pivot points 5 and 6, each of which being secured toone of the elements 2 and 1. In FIG. 1, the jib 2 is shown inclined atan angle A to the horizontal. A thrust force F, or a traction force F,applied to the jib 2 by the jack 4 causes the jib 2 to rotate about axis3. The torque producing this rotation is equal to the product of theforce F (or F) and the length l, which is the distance between axis 3and the line of action of jack 4 (i.e. the direction of the force F orF).

Rotation of jib 2 about axis 3 causes rotation of jack 4 about pivotpoint 6, and this results in a change in the length l. The torqueapplied to the jib 2 by jack 4 is therefore variable, and FIG. 2illustrates the manner in which it varies.

FIG. 2 has the angle A as abscissa and the value C of the moment of theforce F with respect to the pivotal axis which is assumed to beconstant, as ordinate. Curve 7 shows how this moment varies as afunction of the angle A. It can be seen that this moment passes througha maximum value Cm for an angle of inclination A0 corresponding to aposition of jib 2 such that the line of action of jack 4 is at rightangles to the straight line joining axes 3 and 6. In this position, thelength l is at a maximum. The curve 7 is limited to a maximum value Amfor the angle A beyond which the jib cannot travel by reason of itsconstruction. However, curve 7 extends into the region of negativevalues of A, because jib 2 can be inclined below the horizontal.

Curve 8 illustrates the variation in rocking torque Cb of the machine,applied to axis 3, as a function of the angle A. This torque can beregarded as constant.

FIG. 2 shows that with hitherto proposed machines as shown in FIG. 1,the potential maximum work permitted by its construction is notachieved, except when the inclination of the jib is close to A0. Byincreasing the hydraulic pressure in jack 4, that is to say the force-F, a curve such as 9 is obtained in which the central portion thereofis situated beyond the rocking torque Cb of the machine, and this is notallowable. The problem is therefore, not to increase the power of thejack 4 but to raise the extreme portions 7a and 7b of curve 7 whichcorrespond to extreme angles of inclination of jib 2.

The embodiment shown in FIG. 3 causes a flattening of the curve 7. Thefoot of jib 2 is pivotal about shaft 3 which is rigid on structure 1.Jack 4 is connected at 5 and 6 between jib 2 and structure 1. A secondjack 10 is connected between jib 2 and structure 1 at points 11 and 12which constitute pivot points. Axes 5, 6 and 3 on the one hand, and 11,12 and 3 on the other hand, constitute the vertices of two deformabletriangles. Their positions with respect to each other are such that whenjib 2 moves so that axis 11 takes up position 110, thus making thetriangle 11, 12, 3 flat, the axis 5 takes up position 50 so that thetriangle 5, 6, 3 becomes triangle 5a, 6, 3, which is rightangled atvertex 6. In other words, when the line of action of the jack passesthrough axis 3 ofjib 2, so that the torque exerted on jib 2 by jack 10is zero, the line of action of jack 4 is at right angles to the straightline passing through axes 3 and 6. Jib 2 is then at an angle ofinclination A0 corresponding to the maximum moment of force from jack 4with respect to axis 3, and the distance I of this axis from the line ofaction of jack is a maximum and equal to 1m. Because of the hereinbeforedescribed relative arrangement of the various axes 3, 5, 6, 11 and 12,supplementary torque from the second jack 10 is zero when the torquefrom jack 4 is a maximum.

Jacks 4 and 10 are double-acting, and they have two chambers, 4a and 4bin the case of the jack 4, and 10a and 10b in the case of the jack 10.Chambers 4a and 4b are connected to a circuit for supplying andreturning a fluid under pressure through ducts 13 and 14, and chambers10a and 10b are likewise connected to ducts 15 and 16. Each of ducts 15and 16 communicates with a respective one of the two ducts 13 and 14 toform two main supply ducts 17 and 18 which can be made to communicateselectively with a pump 19 or with a return circuit symbolised by areservoir 20 through a distributor 21. Distributor 21 has two routes andthree positions, and it is shown in an inoperative position in FIG. 3. Adistributing and reversing device 22 has two routes and two stablepositions, and it is interposed in the ducts 15 and 16. Device 22defines two sections 150 and 15b in the case ofthe duct 15, and 16a and16b in the case of the duct 16. Device 22 has a slide valve connected toa cam 23 through a rod 24. Cam 23 consists of a disc rotatable about ashaft 26, the disc having a recess with edges 25a and 25b adapted tocooperate with a lug 27 rigid on an end portion 12 of the jack 10. Rod24 is connected to cam 23 by an eccentric finger 28 which is oppositerecess 25 with respect to shaft 26. A resilient member 29, including aspring abutment, is also connected to the finger 28, this abutment beingmounted for pivotal movement about a fixed shaft and tending to create atorque retaining cam 23 to one or other side of the abutment.

Operation of this embodiment will now be described with reference to alifting cycle for the jib 2. The jib 2 initially assumed to be in aposition below the straight line defining the angle A0 shown in FIG. 3.The line of action of jack 10 extends below axis 3. In order to lift thejib 2 fluid is supplied under pressure to chamber 4b of jack 4, and tochamber 10b of jack 10. This is effected by setting distributor 21 tothe position where duct 17 communicates with pump 19. Pump 19 deliversfluid to chamber 4b of jack 4 through duct 14. In the same way duct 16bis pressurized, and the distributing and reversing device 22 is in aposition in which the duct 16b communicates with duct 160. This positionis ensured by rocking cam 23 about shaft 26 when lug 27 engaged edge 25bof recess 25 as triangle l1, 3, 12 became flat. The position ismaintained by spring abutment 29 having rocked about shaft 30 on rockingcam 23.

Fluid under pressure tends to extend jack 4 outwardly, and thereby pushjib 2 upwardly. Chambers 40 and are, of course, in communication withreservoir 20. When jib 2 is at an inclination A0, the pivot points 11and 12 ofjack 10 are aligned with pivot axis 3. Lug 27 then pushes edge25a of recess 25 in cam 23 sufficiently to ensure that the effect ofspring abutment 29 is no longer nullified by alignment of shafts 26 and30 with finger 28. The spring in the abutment is then able to expand,and rotate cam 23 about shaft 26. The resultant rotation drives rod 24and moves the slide valve of the distributing and reversing device 22 toa position in which fluid communication occurs between duct 16b and duct15a. Fluid is then admitted under pressure into chamber 100 of jack 10,and chamber 10b is brought into communication with reservoir 20.

Jack 10 then co-operates in lifting jib 2 by pulling on the jib, and theaction of jack 4 remains as hereinbefore described.

Lowering the jib is effected in the reverse way, a change in theposition of the distributor 21 establishing communication between pump19 and duct 18. This admits fluid under pressure into chambers 4a and10b when the angle of inclination of the jib 2 is greater than the angleA0, and into the chambers 40 and 100 when the angle of inclination isless than A0.

The embodiment shown in FIG. 3 has torque characteristics as shown inFIG. 4, the co-ordinates being the same as in FIG. 2. Curve 7 as shownin FIG. 2 is also shown in FIG. 4, curve 8 corresponding to the rockingtorque. The maximum torque Cm is obtained when the inclination of thejib is A0. Curve 31 shows the variation in torque applied to the footofjib 2 by jack 10. In the direction of increasing values of A, thistorque decreases, becoming zero at A0, and then increasing beyond A0,jack 10 operating under thrust for lifting the jib. The consequenttorque is then of the same sign as the torque from jack 4. As the angleA0 is approached, the distance from the line of action of jack 10 to theaxis 3 decreases, and consequently its torque decreases. When the angleis A0, the torque of the lifting force of jack 10 is zero because theline of action of the jack then passes through axis 3. Beyond A0, jack10 operates under traction because of changes in the position of thedistributing and reversing device 22. The torque of the consequenttraction force is still of the same sign as the force developed by jack4, and its strength increases because the line of action of jack 10moves away from axis 3. The discontinuity in curve 31 at A0 is due tothe change in direction of the lifting force applied to jib 2 by jack10.

Curve 31 added to curve 7 gives curve 32, which shows the variation inthe total lifting torque on a pivoted element including an embodiment ofapparatus in accordance with the invention. The total torque applied tothe foot ofjib 2 of a lifting or Public Works machine is thereforesubstantially constant in the range of use of its jib. By correctlyadjusting the strengths of the torques of which it is composed, byadjustment of the dimensions of the jacks 4 and 10, or by adjustment ofthe pressure of the fluid admitted into each of the jacks, a curve 32 isobtained which can be located close to curve 8, which represents therocking torque of the ma chine. It is then possible to use the machineto its maximum potential while remaining within the safety limitsimposed by its construction, irrespective of the shape and movement ofthe jib.

It will be noted that in the hereinbefore described embodiment inaccordance with the invention, the maximum torque from jack 4 coincideswith zero torque from jack 10.

In other words, the deformable triangle 3, 11, 12 is fiat (H6. 3) whentriangle 3, 5, 6 is right-angled at its vertex 6. The torque from jack 4is reduced by about 30% when the angle at 6 of triangle 3, 5, 6 changesfrom 90 to 45. For example, when the angle of the vertex 6 of triangle3, 5, 6 is 60, the torque from jack 4 is 86% of its maximum value.

In view of this, an increase in the torque lifting jib 2 which isdeveloped by a jack such as 4 can still be satisfactory if a jack suchas 10 is positioned such that the triangle 3, 11, 12 is flat when theangle at 6 of triangle 3, 5, 6 is between 60 and 90 or even 120.However, curve 32 (FIG. 4) will be flatter when the angle at 6 is closerto 90, the desired effect then being at a maximum.

The preceding description has been given with reference to a hydraulicjacks. However, alternative forms using mechanical, electrical or otherlifting means can be used. Apparatus in accordance with the inventioncan be used in the handling and Public Works machine industries.

The hereinbefore described embodiment of the present invention enablesthe inclination of a jib to be altered, using a substantially constantlifting torque. The magnitude of this torque can be adjusted to be veryclose to the rocking torque, and this makes it possible to improve theprofitability and increase the performance of machines equipped withsuch apparatus.

I Claim:

1. Apparatus for changing the inclination of a pivotal element, theelement being pivotal about an axis with respect to a fixed structure,the apparatus comprising a main jack connected between the structure andthe element, and a secondary jack connected between the structure andthe element, the main jack always being on the same side of said pivotalaxis, the points of connection of the respective jacks to said structureand said element, and said pivotal axis constituting the vertices of twodeformable triangles, the deformable triangle of which one side isdefined by the secondary jack being flattened to form a straight linewhen the deformable triangle of which one side is defined by the mainjack is substantially right-angled at its vertex defined by the point ofattachment of said main jack to said structure. I

2. Apparatus according to claim 1, having a circuit for distributing andreturning fluid under pressure, dis tribution and reversing means, anddetector means, and said jacks are hydraulic and double-acting jackswith two chambers, each chamber communicating with the said circuit, thecommunication being direct in the case of the main jack and through saiddistribution and reversing means in the case of the secondary jack, saiddistributing and reversing means being controlled by said detector meansresponsive to the position of the secondary jack with respect to saidpivotal element.

3. Apparatus according to claim 2, having a cam connected to the slidevalve of the said distributing and reversing means and said detectormeans comprises a lug rigid on an end portion of the secondary jack, thelug being arranged to co-operate with said cam, said cam being capableof assuming two stable positions under the action of said lug, thestable positions being maintained by resilient return means, the twostable positions corresponding respectively to positions of thesecondary jack on one or other side of the line defined by the saidflattened triangle.

1. Apparatus for changing the inclination of a pivotal element, theelement being pivotal about an axis with respect to a fixed structure,the apparatus comprising a main jack connected between the structure andthe element, and a secondary jack connected between the structure andthe element, the main jack always being on the same side of said pivotalaxis, the points of connection of the respective jacks to said structureand said element, and said pivotal axis constituting the vertices of twodeformable triangles, the deformable triangle of which one side isdefined by the secondary jack being flattened to form a straight linewhen the deformable triangle of which one side is defined by the mainjack is substantially right-angled at its vertex defined by the point ofattachment of said main jack to said structure.
 2. Apparatus accordingto claim 1, having a circuit for distributing and returning fluid underpressure, distribution and reversing means, and detector means, and saidjacks are hydraulic and double-acting jacks with two chambers, eachchamber communicating with the said circuit, the communication beingdirect in the case of the main jack and through said distribution andreversing means in the case of the secondary jack, said distributing andreversing means being controlled by said detector means responsive tothe position of the secondary jack with respect to said pivotal element.3. Apparatus according to claim 2, having a cam connected to the slidevalve of the said distributing and reversing means and said detectormeans comprises a lug rigid on an end portion of the secondary jack, thelug being arranged to co-operate with said cam, said cam being capableof assuming two stable positions under the action of said lug, thestable positions being maintained by resilient return means, the twostable positions corresponding respectively to positions of thesecondary jack on one or other side of the line defined by the saidflattened triangle.